getData( ){ 
	<b>Future.delayed(Duration(seconds: 5))</b>; 	<em>// 延迟 5s 执行后面的代码</em>
	<b>return</b> '123';
}
<em># 定义一个异步函数<em>
<i>Future &lt;String&gt;</i> request() <b>async</b> {
	String str = <b>await</b> getData( );
	<b>return</b> str
}
<em># 调用，异步返回的数据类型是：<i>Future &lt;String&gt;</i><em>
<i>Future &lt;String&gt;</i> result = request();
<em># 注册监听<em>
result.<b>then</b>( <b>( value )</b> {
	print(value);
})